With a growing demands for open ubiquitous computer systems and multi-venders, various types of connection modes are required in communications systems. For example, there is a need to connect nodes of one local area network (LAN) to nodes of other LANs via wide area networks (WAN) such as the Internet, or wired and wireless telephone networks. In this arrangement nodes can be server computers, workstations, PCs, portable computers, wearable computers, personal digital assistants (PDA), specialized devices, such as sensors and industrial equipment controllers, and peripheral devices such as printers, file systems, and so forth.
As communications networks continue to evolve, so do the protocols used by the various nodes and network components, such as bridges, routers, and gateways, as well as the nodes.
Bridges typically provide physical links between various networks. Routers provide connections between networks by processing up to the network layer of a protocol model to recognize what type of communication devices are connected in the networks, and sending information necessary to destination nodes. Gateways, which can process all of the layers of a protocol model, up to an application layer, convert between an external protocol and an internal protocol of the LAN. Because gateways are protocol conversion systems, which process layers up to the application layer, designing the gateways is complex and can take a long time.
Various protocol models are known, such as the open system interconnection (ISO) model, and the TCP/IP model 400 shown in FIG. 4. Generally, models include application layers 401, and network layers 402. The network layers 402 can include transport (TCP, UDP), internet (IP, ICMP), network interface (ARP, RARP), and hardware (Ethernet, NIC) layers. The application layers 401 can include FTP, TELNET<E-mail, SNMP, SOAP, uPnP, http, and device specific layers.
FIG. 1 shows a typical prior art network arrangement 100. The arrangement includes an external node 101, a wide area network (WAN) 110, e.g., the Internet, a gateway 120, a local area network (LAN) 130, and an internal node 102. A first protocol 111 is used “outside” the gateway 120, and a second protocol 131 is used “inside” the gateway. Therefore, the gateway 120 includes a protocol converter 121.
Typically, the gateway 120 “hides” the internal node 102 from the external node 101. This is intentional for security reasons. Therefore, the external node cannot discover the address of the internal node. Instead, the external node has a proxy address provided by the gateway, and the external node can only communicate indirectly with the internal node via this proxy address. Obviously, should the gateway fail, communications with the external node likewise fails. In addition, this arrangement makes it difficult to integrate many different converters for multiple protocols in the gateway 120.
In ubiquitous network environments, it is desired that any node can communicate with any other node in the network, with or without going through a gateway. Also, many standard application protocol layers 401 are used, such as SOAP, uPnP, and http. All of these require processing above the network layers 402. However, small specialized nodes, such as remote sensors or industrial controllers, have limited storage and processor capabilities. This makes it difficult to implement all of the necessary protocol stack in nodes with a “small memory footprint.” In addition, it is desired that these devices can with other nodes without having to pass through gateway. Therefore, there is a need for a protocol conversion strategy which can alleviate the problems of the prior art.